<!DOCTYPE html>
<html>

	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>

	<body>
		<button id="btn" onclick="dbtn()">点击</button>
		<script type="text/javascript">
			/*function dbtn() {
				afunc(bfunc)
			}

			function afunc(callback) {
				var a = 3;
				callback(a)
			}

			var bfunc = function(e) {
				console.log(e)
			}*/
			
			function dbtn() {
				console.log(cfunc);
			}
			
			function cfunc () {
				var a =1;
				
			}
			
		</script>
	</body>

</html>